This invention relates to seat recliners of the type having a rotatable pawl engagable with a sector gear and a cam for holding the pawl in locking engagement with the sector gear. In particular, the present invention provides improved to the seat back.
Numerous recliner mechanisms have been developed for adjusting the angle of a seat back. One type of mechanism includes a sector gear, attached to the seat back, consisting of a plate with a tooth portion along one edge. The tooth portion is curved with a center of curvature at the rotational axis of the seat back. A locking pawl is mounted to a side plate which in turn is attached to the lower seat cushion and has a corresponding arcuate toothed portion. The pawl is rotatable into and out of engagement with the teeth of the sector gear so as to lock and unlock the seat back. A cam, also rotatably mounted to the side plate attached to the seat cushion, engages a camming surface of the pawl to hold the pawl in position engaged with the sector gear to latch the seat back in place. Typically, the cam is biased into a locking position to keep the seat back locked. To adjust the seat back angle, an operating lever is provided to rotate the cam to a release position enabling the pawl to disengage from the sector gear to enable rotation of the seat back.
In some recliners the camming surface may include a cam and the pawl produces sufficient friction to lock the cam in place. However, if the cam engages the camming surface ,; outside of the locking zone the friction between the cam and pawl is not sufficient to prevent sliding of the cam across the camming surface. In other words, the cam and pawl have a limited range of positions at which the cam and pawl will engage to lock the pawl with the sector gear.
One reason for making a limited range of locking positions is so the release lever, which is coupled to the cam, can have a rest position within a narrow tolerance range specified by the seat customer. However, due to tolerance variations in the cam, pawl and sector gear and the tolerance in the location of the various pivot points, the cam and pawl may not engage at the locking zone with the pawl teeth fully engaged with the sector gear teeth. When contact occurs outside of the locking zone, there may be insufficient friction to hold the cam in place. Forces applied to the seat back may "backdrive" the cam, causing the cam to slip off the pawl camming surface, releasing the pawl and seat back.
Accordingly, it is an object of the present invention to provide a recliner with an enlarged locking zone, giving the recliner a wider tolerance range for the positions of the cam and pawl to lock the seat back in place.
It is a further object of the present invention to provide means for controlling the position of the release handle at rest regardless of the cam position.
It is another object of the invention to provide a quick release recliner that positively disengages the pawl from the sector gear rather than relying solely on gravity to drop the pawl.
The recliner of the present invention includes a base plate attached to the lower seat cushion, an arm mounted to the seat back and pivotally coupled to the base plate for rotation of the arm and seat back relative to the base plate, a sector gear attached to the arm, a pawl rotatably mounted to the base plate engagable with the teeth of the sector gear to lock the arm in place, a cam rotatably mounted to the base plate and engagable with a camming surface of the pawl to hold the pawl in engagement with the sector gear and an operating lever to move the cam to a release position to disengage the pawl from the sector gear. The entire camming surface of the pawl is a locking zone such that the cam and pawl will lock regardless of where the cam contacts the pawl. This is accomplished by forming the camming surface with a constant radius arc so that the locking angle between the cam and pawl is substantially constant over the entire camming surface. This ensures locking engagement between the cam and pawl with the pawl teeth fully engaged with the sector gear teeth.
The release lever is coupled to the cam through a slotted coupling enabling initial rotation of the lever before the cam begins to move. This allows the release lever to have a predefined rest position relative to the base plate regardless of the cam rest position.
The cam is profiled to clear the pawl quickly once the cam as disengaged from the pawl. To ensure positive release of the pawl, the cam, once it has cleared the camming surface, engages a release portion of the pawl to rotate the pawl out of contact with the sector gear.